Women who take the oral contraceptive medication are known to have an increased incidence of cholesterol cholelithiasis and gallbladder disease. The composition of gallbladder bile was investigated in 22 women during a period without contraceptive usage. Gallbladder bile lipid composition as well as bile acid composition were investigated during these two respective periods. The major findings were an increase in biliary lithogenicity in the women during periods of contraceptive usage. In addition, when oral contraceptives were discontinued, gallbladder bile became significantly less lithogenic. These studies indicate that the potential for cholesterol cholelithiasis is increased in women taking oral contraceptive medications.